In current storage networks, and particularly storage networks including geographically distributed directors (or nodes) and storage resources, preserving or reducing bandwidth between resources and directors while providing optimized data availability and access is highly desirable. Data access may be localized, in part, to improve access speed to pages requested by host devices. Caching pages at directors provides localization, however, it is desirable that the cached data be kept coherent with respect to modifications at other directors that may be caching the same data. An example of a system for providing distributed cache coherence is described in U.S. Patent App. Pub. No. 2006/0031450 to Unrau et al., entitled “Systems and Methods for Providing Distributed Cache Coherency,” which is incorporated herein by reference. Other systems and techniques for managing and sharing storage array functions among multiple storage groups in a storage network are described, for example, in U.S. Pat. No. 7,266,706 to Brown et al. entitled “Methods and Systems for Implementing Shared Disk Array Management Functions,” which is incorporated herein by reference.
Data transfer among storage devices, including transfers for data replication or mirroring functions, may involve various data synchronization processing and techniques to provide reliable protection copies of data among a source site and a destination site. In synchronous transfers, data may be transmitted to a remote site and an acknowledgement of a successful write is transmitted synchronously with the completion thereof. In asynchronous transfers, a data transfer process may be initiated and a data write may be acknowledged before the data is actually transferred to directors at the remote site. Asynchronous transfers may occur in connection with sites located geographically distant from each other. Asynchronous distances may be distances in which asynchronous transfers are used because synchronous transfers would take more time than is preferable or desired. Particularly for asynchronous transfers, it is desirable to maintain a proper ordering of writes such that any errors or failures that occur during data transfer may be properly identified and addressed such that, for example, incomplete data writes be reversed or rolled back to a consistent data state as necessary.
Reference is made, for example, to U.S. Pat. No. 7,475,207 to Bromling et al. entitled “Maintaining Write Order Fidelity on a Multi-Writer System,” which is incorporated herein by reference, that discusses features for maintaining write order fidelity (WOF) in an active/active system in which a plurality of directors (i.e. controllers and/or access nodes) at geographically separate sites can concurrently read and/or write data in a distributed data system. Discussions of data ordering techniques for synchronous and asynchronous data replication processing for other types of systems, including types of remote data facility (RDF) systems produced by EMC Corporation of Hopkinton, Mass., may be found, for example, in U.S. Pat. No. 7,613,890 to Meiri, entitled “Consistent Replication Across Multiple Storage Devices,” U.S. Pat. No. 7,054,883 to Meiri et al., entitled “Virtual Ordered Writes for Multiple Storage Devices,” and U.S. patent application Ser. No. 12/080,027 to Meiri et al., filed Mar. 31, 2008, entitled “Active/Active Remote Synchronous Mirroring,” which are all incorporated herein by reference.
In a virtualized environment, a centralized management infrastructure, henceforth referred to as a virtual center, may provide a central point of control for managing, monitoring, provisioning and migrating virtual machines. A virtual machine (VM) is a software implementation of a machine that executes programs like a physical machine. Virtualization software allows multiple VMs with separate operating systems to run in isolation on the same physical server. Each VM may have its own set of virtual hardware (e.g., RAM, CPU, NIC, etc.) upon which an operating system and applications are loaded. The operating system may see a consistent, normalized set of hardware regardless of the actual physical hardware components. The virtual center may operate to control virtual machines in data centers and, for example, in connection with cloud computing. The virtual center may further include a virtual data center that provides logical control and management of data storage in a data center, and provides for sub-dividing contents of virtual components into compute resources, network resources and storage resources. Under various circumstances, it may be advantageous to control access to resources among the virtual components, including sharing of distributed resources among the virtual components.
A distributed storage system of a virtualized environment may include a grid, and/or other configuration, of different storage nodes connected to each other over synchronous and/or asynchronous latencies. Coordinating and controlling the sharing of resources distributed among these different storage nodes may, in many cases, be difficult or problematic using known technologies.
Accordingly, it is desirable to provide an effective and efficient system to address issues like that noted above for a distributed system in a virtualized environment.